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What is Super Missile Rod?

I had a gentleman stop by the shop last night to look at a chassis that I had for sale. He asked about the construction material and I explained that it was 4130N using the GTAW process using ER80S-d2 rod. He asked me why I chose to use that particular rod and I explained that it was the closest match to the 4130 in strength yet still alow some elongation and not have to be heat treated.

He informed me that ALL the high end builders are using Super Missile Rod. I have heard that term a couple of times before and just dismissed it. Does anyone know what this Super Missile Rod is that EVERYONE is using? Thanks, Mike.

When it comes to welding 4130, doing something because "all the high end builders" are supposedly doing it is not the way to go. Go find a shop that not only builds sprint cars, but has had one of their sprint cars crash. See how their cage held up (look for breaks near the welds). BTW, not all round-n-round race cars are built out of 4130.
You might want to look at this:http://web.a-znet.com/~dave1w/maxim_disaster.htm
Even though the author claims all the breaks were "in the weld" if you look closely you will see that most (if not all) the breaks were immediately next to the weld.

So here are a couple of facts:
1) Most roll cages are never actually tested (thank god).
2) There is precious little information about post crash 4130 roll cages. The most famous seems to be the John Force crash, but NHRA has been relatively silent about it. I suspect if NHRA knew something definitive they would publish/update their rule books accordingly.
3) Most 4130failure do not happen in the weld bead, but right next to it (within an inch). This suggest that technique, in light of 4130's susceptibility to hardening, is more of an issue than any filler rod. Please don't pick a magic filler rod and assume all is good.

Keep in mind, most drag racers never crash hard - so they don't know if their cage is any good. Also keep in mind, John Force's funny car broke in half - and that was arguably built by the best shop money could buy (supposedly they even have an oven to stress relieve the whole chassis).

When using TIG (or I suppose MIG) to weld 4130, the only real discussions I have seen is using either ER80S-d2 (Lincoln Electric) or ER70S-2http://www.netwelding.com/Welding%204130.htm. The ER80S seems to be a better choice if you need to match strength - particularly important if you are welding say plate, and then try to bend test it (grinding the weld flat). The argument for ER70S is that you make the fillet a little bigger to make up for reduce tinsel strength - NHRA doesn't allow grinding of the welds anyway.

Corner joints should be gusseted. Design the joints correctly!

Normalize 4130is something like 90+ ksi. When you have tight fitup you will mix the filler with the base material and because of the relatively rapid cooling, you will get some hardening. The ER80 will match close, the ER70 is a bit undermatched after mixing/dilution.

As for using a stainless steel rod - it will definitely work. Missle rod is typically 312 stainless, which is a pretty forgiving rod. I like 309 with its high nickle content. But then again I don't weld critical parts with it (it hasn't happened but consider mild steel exhaust flange to 304 stainless pipe cracking - bit of noise at worst).

I suspect in all but professional racing classes, you would be better off finding a more forgiving material. The problem with 4130 is that if something is wrong, you may not find out till its too late.

Thanks for all of your replies. I guess I could have done more research on it. I just thought I would throw it out there and see what kind of response it got.

As far as myself, in my shop I use the ER80S-d2 rod and have had great results for the last 8 years or so that I have been using it. I am just always interested to hear what others in the industry are using/doing.

I did think it was kind of odd that if this gentlemen knew so much about welding and fabricating, why was he looking at purchasing one of my chassis? Mike.